Modern UV-lithography is searching for new highly parallel writing concepts. Spatial light modulation (SLM) with optical MEMS devices offers such possibilities. Special emphasis must be put on the ability of SLM devices to handle ultraviolet light (UV), deep ultraviolet light (DUV) and extreme ultraviolet light (EUV).
A SLM chip may comprise a DRAM-like CMOS circuitry with several million individually addressable pixels on top. Said pixels are deflected due to an electrostatic force between a mirror element and an address electrode.
For good performance of the SLM chip almost every single pixel must work and moreover they must respond to an applied voltage similarly enough to be able to compensate for the differences by calibration.
Using a white light interferometer has earlier created a map of defective pixels. Software identified the individual pixels and calculated the deflection angles automatically. Such a method finds quite well not only fabrication errors, but also additional errors that occurred during operation. On the other hand such method is rather slow, as a high magnification implies that many images have to be taken. As the size of the SLM chips are growing, and thereby the number of pixels, more and more pixels has to be analyzed. Preferably the SLM chips also have to be analyzed in a faster way than what is done today. Therefore, what is needed in the art is a faster way to get information about defective pixels of a particular SLM chip.